q

Q is the 17th letter of the Latin alphabet. It is written as uppercase Q or lowercase q and is used in English and many other languages to represent a /k/ or /kw/ sound, depending on context. In English, the letter almost always appears with the letter U to form the /kw/ sequence, as in quick or question, though there are exceptions in borrowed or transliterated words.

The letter's name in English is pronounced “cue.” Its origins lie in the Phoenician letter qoph, passed to the Greek script (where a form called koppa existed) and finally adopted into Latin, which used Q to represent the /k/ sound before vowels and, in the digraph qu, the /kw/ sound.

Q is among the least frequent letters in English, and it is more common in loanwords from French and other languages. Beyond the Latin alphabet, Q appears in various scripts and alphabets with different values and uses, depending on the language and context.

In mathematics, Q denotes the set of rational numbers. In physics and engineering, Q is used for electric charge and, in thermodynamics, for heat transfer (Q often stands for heat). In electronics, the quality factor Q describes resonance. In computing and quantum discussions, Q is sometimes used to symbolize quantum concepts or qubits; the programming language Q is used with the kdb+ database for time-series analysis.

Culturally, Q is the gadget-master in the James Bond franchise, head of Q Branch, known for supplying Bond with demonstrations of futuristic devices.

Unicode representation: uppercase Q is U+0051 and lowercase q is U+0071.